Frequency selective transmission line



Feb. 24, 1942. H. o. ROOSENSTEIN 3 5 FREQUENCY SELECTIVE TRANSMISSION LINE Filed Dec. 31, 1938 M M Li 1 2;

- INVENTOR. #41:?77'0 RO0SENSTE/N BY A TTORNEY.

Patented Feb.24, 1942 I UNITED STATES PATENT OFFICE- rasquancr smwva TRANSMI-ssmli Drahtlose my, a corporation of Application December-s1. 1m. sci-n1 No. 24304- In Germany-January 27,1938

4 Claims. (Cl. 17H!) The invention is concerned with a two-wire line for ultra short waves which insures a band pass filter efiect by virtue of its special resonance properties. In order to raise the selectivity of a tuned two-wire line. it is known in the art to *bridge the double-wire line at. the nodal points of the standing waves" arising upon it. It has also been suggested'in the earlier art not to place such bridging means exactly in the nodal points .of a wave corresponding to. a mean frequency,

with a view to insuring a band-pass filter effect, but rather at unlike distances somewhat laterally thereof to thus result in a sort or arrangement'oomprising a seriation of dissimilarly tuned .rentsare flowing, and, moreover, that in casev of conductive bridging 'it is notpossible to separate the two conductors for direct current,

Contradistinct to the prior'art, the'present invention is concerned with a double-wire line broadening of the resonance curve. According to the invention, spaced roughly-a half wave-'- length (ll/2.) apartare connected series imped ances whereby theline is divided into a plurality of circuits being connected with .oneanother. The impedances which may be considered for. the said purpose may be desired series impedances at all, such as; for instance, capacities or tuned oscillation circuits; Because of the vductors of a tuned Lecher wire line.

rammemansn m ow Germany or any other waves, of the band to be transmitted, but rather irregular distances awaytherefrom. In other words, by using diflerent values for diiferent condensers, we obtain. differently tuned circuits: likewise, by means of unequal spacing between condensers, we obtain different values-of inductance of the conductor between condensers and thus again obtain circuits tuned to diiferent frequencies.

Figs. 1 and 2 show twoexemplifled embodiments of the invention.

Referring to Fig. 1, 1 and 2 are the two con- The os- 'cillations to be transmittedare then fed to these with parallel-connected inductances to result in out, it is possible to secure band-pass filter acrequisite loose coupling, the resistance ofthe same must, of course, be high. If. there is'only pass filter action which corresponds to -the wellknown, eflect of two intercoupled oscillation circuits tuned to one and the same wave. The same band-pass filter action could also be obtained by. making the spacing of the series impedances from one another difierent; in other words, by mounting the impedances not exactly in the conductors at one end, whilethe transmitted oscillations are put out at the opposite end thereof. Hence, this line could be conceived to be a quadripole, or four-terminal network. Included in the line are the capacities C1, Cs; C1, C2, etc., which represent the series impedances of the in vention. These capacities could be combined tuned circuits, with a view to raising their imwhich is free fromihe said drawbacks and which 25 If a coaxial line rather than a parallel ,wire

-is adapted to raise the selectivity as well asth'e I line is used, it will be advantageous to include series impedances only in the inner conductor, as shown in Fig, 2, where l is the inner conductor, 2 the envelope surrounding the inner conductor. C1, C2, the series impedances. As already pointed and disclosed in the prior art. This does away with an appreciable source of losses, and this is an outstanding advantage of the invention.

The invention is not restricted to the exe'mplifled embodiments here illustrated. In fact, it consists, broadly, in the fact that'impedances are .connected in series in a two-wire line at distances roughly one-half wavelength or a mul-' tiple 'of M2.

What is claimed is: v

1.1A selective coaxial line for the transmission of high frequency oscillations comprising an inner conductor having spaced condensers serially inserted therein, said condensers being arranged substantially at potential anti-nodal points along potential loops or anti-nodes of'the mean wave, said conductor and havingsuch values as to combine with the sections of inner conductor between them to form tuned circuits;

2. A line in accordance with claim 1, characterized in this that said condensers have diflerent values whereby a band-pass characteristic is obtained.

3. A line in accordance with claim 1 for carrying a band of frequencies characterized in this that the spacing between condensers varies about the mean value of the spacing whereby a band 10 conductor.

pass characteristic is obtained.

HANS o'rro ROOSENSTEIN. 

